[ACCEPTED]-(Deep) copying an array using jQuery-jquery

Accepted answer
Score: 292

Since Array.slice() does not do deep copying, it 7 is not suitable for multidimensional arrays:

var a =[[1], [2], [3]];
var b = a.slice();

b.shift().shift();
// a is now [[], [2], [3]]

Note 6 that although I've used shift().shift() above, the point 5 is just that b[0][0] contains a pointer to a[0][0] rather than a value.

Likewise 4 delete(b[0][0]) also causes a[0][0] to be deleted and b[0][0]=99 also changes 3 the value of a[0][0] to 99.

jQuery's extend method does perform 2 a deep copy when a true value is passed 1 as the initial argument:

var a =[[1], [2], [3]];
var b = $.extend(true, [], a);

b.shift().shift();
// a is still [[1], [2], [3]]
Score: 31

$.extend(true, [], [['a', ['c']], 'b'])

That should do it for you.

0

Score: 21

I realize you're looking for a "deep" copy of an array, but if you just have a single level array you can use this:

Copying a native JS Array is easy. Use the 5 Array.slice() method which creates a copy of part/all 4 of the array.

var foo = ['a','b','c','d','e'];
var bar = foo.slice();

now foo and bar are 5 member 3 arrays of 'a','b','c','d','e'

of course bar 2 is a copy, not a reference... so if you 1 did this next...

bar.push('f');
alert('foo:' + foo.join(', '));
alert('bar:' + bar.join(', '));

you would now get:

foo:a, b, c, d, e
bar:a, b, c, d, e, f
Score: 13

Everything in JavaScript is pass by reference, so 4 if you want a true deep copy of the objects 3 in the array, the best method I can think 2 of is to serialize the entire array to JSON 1 and then de-serialize it back.

Score: 7

If you want to use pure JavaScript then 1 try this:

 var arr=["apple","ball","cat","dog"];
 var narr=[];

 for(var i=0;i<arr.length;i++){
     narr.push(arr[i]);
 }
 alert(narr); //output: apple,ball,vat,dog
 narr.push("elephant");
 alert(arr); // output: apple,ball,vat,dog
 alert(narr); // apple,ball,vat,dog,elephant
Score: 3

how about complex types? when array contains 3 objects... or any else

My variant:

Object.prototype.copy = function(){
    var v_newObj = {};
    for(v_i in this)
        v_newObj[v_i] = (typeof this[v_i]).contains(/^(array|object)$/) ? this[v_i].copy() : this[v_i];
    return v_newObj;
}

Array.prototype.copy = function(){
    var v_newArr = [];
    this.each(function(v_i){
        v_newArr.push((typeof v_i).contains(/^(array|object)$/) ? v_i.copy() : v_i);
    });
    return v_newArr;
}

It's not 2 final version, just an idea.

PS: method each 1 and contains are prototypes also.

Score: 2

I've come across this "deep object 3 copy" function that I've found handy 2 for duplicating objects by value. It doesn't 1 use jQuery, but it certainly is deep.

http://www.overset.com/2007/07/11/javascript-recursive-object-copy-deep-object-copy-pass-by-value/

Score: 2

I plan on releasing this code in the next 6 version of jPaq, but until then, you can use 5 this if your goal is to do a deep copy of 4 arrays:

Array.prototype.clone = function(doDeepCopy) {
    if(doDeepCopy) {
        var encountered = [{
            a : this,
            b : []
        }];

        var item,
            levels = [{a:this, b:encountered[0].b, i:0}],
            level = 0,
            i = 0,
            len = this.length;

        while(i < len) {
            item = levels[level].a[i];
            if(Object.prototype.toString.call(item) === "[object Array]") {
                for(var j = encountered.length - 1; j >= 0; j--) {
                    if(encountered[j].a === item) {
                        levels[level].b.push(encountered[j].b);
                        break;
                    }
                }
                if(j < 0) {
                    encountered.push(j = {
                        a : item,
                        b : []
                    });
                    levels[level].b.push(j.b);
                    levels[level].i = i + 1;
                    levels[++level] = {a:item, b:j.b, i:0};
                    i = -1;
                    len = item.length;
                }
            }
            else {
                levels[level].b.push(item);
            }

            if(++i == len && level > 0) {
                levels.pop();
                i = levels[--level].i;
                len = levels[level].a.length;
            }
        }

        return encountered[0].b;
    }
    else {
        return this.slice(0);
    }
};

The following is an example of how 3 to call this function to do a deep copy 2 of a recursive array:

// Create a recursive array to prove that the cloning function can handle it.
var arrOriginal = [1,2,3];
arrOriginal.push(arrOriginal);

// Make a shallow copy of the recursive array.
var arrShallowCopy = arrOriginal.clone();

// Prove that the shallow copy isn't the same as a deep copy by showing that
// arrShallowCopy contains arrOriginal.
alert("It is " + (arrShallowCopy[3] === arrOriginal)
    + " that arrShallowCopy contains arrOriginal.");

// Make a deep copy of the recursive array.
var arrDeepCopy = arrOriginal.clone(true);

// Prove that the deep copy really works by showing that the original array is
// not the fourth item in arrDeepCopy but that this new array is.
alert("It is "
    + (arrDeepCopy[3] !== arrOriginal && arrDeepCopy === arrDeepCopy[3])
    + " that arrDeepCopy contains itself and not arrOriginal.");

You can play around 1 with this code here at JS Bin.

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